The overall objective of the proposed research is to learn how the behavioral effects of psychomotor stimulants are determined by an individual's past experiences with specific social and aggressive behavior. We propose to investigate to what extent past experiences with aggressive, submissive, sexual or maternal behavior modulate neural processes that are critical for subsequent behavioral effects of psychomotor stimulants. Alternatively, we will be studying how pharmacological experiences, particularly with opiate agonists, modulate the neural processes that are the targets for the effects of psychomotor stimulants. Withdrawal from continuous exposure to opiates will be a focus of our studies since it is associated with heightened aggression and with hypersensitivity to drugs that act on brain catecholamines. After a specific behavioral or pharmacological history has been established, the initial strategy will rely on challenging an individual pharmacologically during a range of behavioral tasks. The "behavioral assays" include measures of reflexive responses as well as complex social and aggressive behaviors, and schedule-controlled behavior. When indicated from the pharmacological studies we will assay specific brain regions in which catecholamines and opioid peptides are localized in order to learn about direct neurochemical changes that are associated with behavioral drug effects. A further aim of the proposed work concerns the detailed quantitative analysis of drug action on complex social and aggressive behavior. By using computerized recording techniques, the moment-to-moment details of drug-altered behavior are accurately measured. This information promises to more precisely delineate the mediating neurobiological mechanisms for psychomotor stimulant effects on aggression.